Carlos Alcaraz got his Croatia Open title defence off to a strong start with a straight-sets victory over Norbert Gombos on Thursday.

The Spaniard, who this week became the second-youngest player to break into the top five of the ATP rankings this century, behind only compatriot Rafael Nadal, saw off Gombos 6-2 6-3 in Umag.

Alcaraz, handed a first-round bye, will now face Facundo Bagnis in the last eight after the Argentinian beat Corentin Moutet 6-3 6-1.

Despite the straightforward nature of his victory over Gombos, the top seed was regularly tested on his own serve.

"It was a really tough match," said Alcaraz, whose triumph in Umag last year marked his first ATP Tour-level title.

"It wasn't as easy as the result seems. Norbert played a really good game and the first round of every tournament is never easy. 

"I had to get used to the conditions. It was tough for me, but at the end I found a way to play better and get the win."

Franco Agamenone also advanced to his first ATP Tour quarter-final with a 3-6 6-1 7-5 comeback over Sebastian Baez, while Marco Cecchinato upset Lorenzo Musetti 6-4 6-3.

At the Austrian Open, Dominic Thiem was eliminated in the quarter-finals of his home tournament by Yannick Hanfmann, the former world number three going down 6-4 3-6 6-4 in a rain-affected contest.

Roberto Bautista Agut prevailed 4-6 7-5 7-5 against Jiri Lehecka in a match lasting nearly three hours. A meeting with fellow Spaniard Albert Ramos-Vinolas, who defeated Pedro Martinez 6-4 6-2, is his reward.